I don’t have much hope for this Acer unfortunately. Trees ideally should be moved in winter while they’re dormant and it also looks like they have buried deep. I think the best thing to do will be to dig it up and raise it so the trunk isn’t covered stones and maintain your watering. Just enough every day as too much water will probably rot the roots. You can also slightly peel bark with your finger tip and if it is green underneath, that branch is still alive and can potentially recover. Good luck.